Recombinant Sulfolobus islandicus UPF0290 protein M1425_1364 (M1425_1364)

What is Sulfolobus islandicus and why is it significant for research?

Sulfolobus islandicus is a hyperthermophilic archaeon belonging to the phylum Crenarchaeota. This organism has gained significant attention in research due to its ability to thrive in extreme environments such as volcanic springs with temperatures approaching 91°C. S. islandicus has rapidly developed as a model organism for studying archaeal biology and serves as an excellent system for linking novel biological processes to evolutionary ecology through functional population genomics . The extremophilic nature of this organism makes it particularly valuable for studying proteins with potential applications in high-temperature industrial processes and as a window into the biology of early life forms that may have existed in extreme conditions.

What are the basic characteristics of the UPF0290 protein M1425_1364?

The UPF0290 protein M1425_1364 from Sulfolobus islandicus (UniProt ID: C3MVC3) is a full-length protein consisting of 166 amino acids. Its complete amino acid sequence is: MSIAYDLLLSILIYLPAFVANGSGPFIKRGTPIDFGKNFVDGRRLFGDGKTFEGLIVALTFGTTVGVIISKFFTAEWTLISFLESLFAMIGDMIGAFIKRRLGIPRGGRVLGLDQLDFVLGASLILVLMRVNITWYQFLFICGLAFFLHQGTNYVAYLLKIKNVPW . The protein is also known by several synonyms including carS, CDP-archaeol synthase, and CDP-2,3-bis-(O-geranylgeranyl-sn-glycerol synthase, suggesting its potential role in lipid biosynthesis pathways . The UPF0290 designation indicates it belongs to a family of proteins with as-yet uncharacterized functions, making it an intriguing target for fundamental research into archaeal biochemistry.

How is the recombinant version of this protein produced and what are its specifications?

The recombinant UPF0290 protein M1425_1364 is produced by expressing the Sulfolobus islandicus gene in E. coli with an N-terminal His-tag fusion. The resulting protein covers the full length of the native sequence (amino acids 1-166) with the addition of the His-tag to facilitate purification. The final product is supplied as a lyophilized powder with greater than 90% purity as determined by SDS-PAGE analysis . The recombinant product is stored in a Tris/PBS-based buffer containing 6% Trehalose at pH 8.0, which helps maintain protein stability during storage and reconstitution .

What is the recommended protocol for reconstitution and storage of the recombinant protein?

The recommended reconstitution protocol is as follows:

• Centrifuge the vial briefly before opening to ensure all contents are at the bottom

• Reconstitute the lyophilized protein in deionized sterile water to a concentration of 0.1-1.0 mg/mL

• Add glycerol to a final concentration of 5-50% (recommended default is 50%)

• Aliquot the reconstituted protein for long-term storage

For storage:

• Store the lyophilized powder at -20°C/-80°C upon receipt

• Store reconstituted aliquots at -20°C/-80°C for long-term storage

• Working aliquots can be kept at 4°C for up to one week

• Avoid repeated freeze-thaw cycles as they can compromise protein activity

How can researchers verify the functionality of the recombinant UPF0290 protein?

For functional verification of the UPF0290 protein, researchers should design assays based on its predicted function as a CDP-archaeol synthase. This would typically involve:

• Enzymatic activity assays measuring the conversion of substrates (such as CDP-diacylglycerol and archaeol precursors) to products

• Binding assays to determine interaction with predicted substrates using techniques such as isothermal titration calorimetry (ITC) or surface plasmon resonance (SPR)

• Structural analysis using circular dichroism (CD) to confirm proper protein folding

• Thermal stability assays to verify the protein retains its hyperthermophilic properties

• Complementation studies in S. islandicus strains with deleted or mutated native carS gene to demonstrate functional rescue

When designing these assays, it's critical to include appropriate controls and consider the extreme temperature optima (around 75-80°C) at which this protein would naturally function.

What experimental conditions are optimal for working with proteins from Sulfolobus islandicus?

When working with proteins from hyperthermophilic archaea like S. islandicus, the following experimental conditions should be considered:

For culture conditions when working with living S. islandicus, researchers typically use specialized media such as basic salts medium or 2x SCV medium, with incubation at 75-78°C . When performing transformation procedures, electroporation is commonly used, followed by recovery in pre-warmed media and plating on Gelrite® plates since traditional agar would melt at these high temperatures .

What genetic markers and tools are available for manipulating Sulfolobus islandicus?

Several genetic markers and tools have been developed for S. islandicus:

• The pyrEF gene: Historically, this was the primary selection marker used in S. islandicus genetic studies, enabling selection based on uracil prototrophy/5-FOA resistance .

• The apt gene: This newer genetic marker addresses limitations of the pyrEF system, particularly for strains already lacking the pyrEF gene. The apt marker allows for counterselection using 6-methylpurine, expanding the toolkit for genetic manipulation .

• The argD gene: Used alongside pyrEF in mating assays, this marker enables selection based on agmatine prototrophy .

• CRISPR-Cas systems: Native type III CRISPR-Cas systems have been adapted for genome editing. These require identifying appropriate protospacers in the target gene, with the recognition that type III systems function only when the crRNA is complementary to a transcript .

• Plasmid-based tools: Several conjugative plasmids have been characterized in S. islandicus, including pM164, which can be used for gene transfer with high efficiency .

These tools collectively enable a range of genetic manipulation approaches, from knockout studies to gene replacements and marker insertions.

How can the CRISPR-Cas system be employed for genome editing in Sulfolobus islandicus?

The CRISPR-Cas system for genome editing in S. islandicus involves several methodical steps:

• Protospacer selection: Identify a suitable protospacer (approximately 39 nt long) on the template strand of the target gene. For type III CRISPR systems in S. islandicus, the crRNA must be complementary to a transcript for the system to function properly .

• Spacer construction: Create a spacer based on the selected protospacer by mixing complementary oligonucleotides, heating to 95°C for 10 minutes, and gradually cooling to room temperature. The resulting dsDNA will have 3 nt protruding ends suitable for ligation .

• Vector construction: Ligate the spacer into an appropriate vector (such as linearized pGE1 at the LguI site) to create a mini-CRISPR array .

• Donor DNA preparation: Generate donor DNA fragments containing the desired mutation or deletion using overlap extension PCR. These fragments provide the template for homology-directed repair after CRISPR-induced breaks .

• Transformation: Transform S. islandicus with the constructed plasmids using electroporation. Immediately after electroporation, transfer cells into pre-warmed basic salts medium and incubate at 75°C for 30 minutes without shaking .

• Selection and verification: Plate transformed cells on appropriate selective media and incubate at 78°C for 5-7 days. Verify successful genome editing through PCR and sequencing .

This approach enables precise genetic modifications in S. islandicus, allowing researchers to study gene function in this hyperthermophilic archaeon.

What are effective methods for gene transfer in Sulfolobus islandicus?

For effective gene transfer in S. islandicus, researchers can employ several approaches:

• Electroporation-based transformation:

  • Prepare competent cells (OD600 around 10)

  • Mix 500 ng DNA with 50 μL competent cells

  • Perform electroporation at room temperature

  • Immediately transfer cells to pre-warmed media

  • Incubate at 75°C for recovery

  • Plate on Gelrite® plates with appropriate selective media

• Conjugation using natural plasmid transfer:

  • Grow both donor and recipient strains to mid-log phase

  • Equalize optical density (OD600 of 0.3) using warm media

  • Mix strains in equal parts and incubate at room temperature for 15 minutes

  • Incubate mixed cultures under shaking conditions (180 rpm) at 76°C overnight

  • Wash cells to remove selection compounds

  • Plate on appropriate selective media

• Plasmid-mediated high-frequency recombination:

  • Utilize conjugative plasmids like pM164 that integrate at specific tRNA sites

  • The TraG protein is essential for conjugation efficiency (deletion of traG reduces transfer efficiency to approximately 1%)

  • Conjugative plasmids can drive localized high-frequency recombination near their integration sites

  • Verification of successful transfer can be performed using PCR amplification of the integration site

These methods provide researchers with multiple options for introducing genetic material into S. islandicus, enabling various genetic studies and manipulations.

How does the UPF0290 protein M1425_1364 function in the context of Sulfolobus islandicus biology?

Based on its annotation as CDP-archaeol synthase (carS), the UPF0290 protein M1425_1364 likely plays a crucial role in the lipid biosynthesis pathway of S. islandicus . In archaea, particularly in extremophiles like Sulfolobus, membrane lipids have unique structures that contribute to their ability to withstand extreme conditions. The archaeol lipids typically contain ether linkages between glycerol and isoprenoid chains, rather than the ester linkages found in bacteria and eukaryotes.

As a CDP-archaeol synthase, this protein would catalyze a key step in membrane lipid biosynthesis:

$\text{CDP-diacylglycerol} + \text{archaeol} \rightarrow \text{CDP-archaeol} + \text{diacylglycerol}$

The resulting CDP-archaeol serves as a precursor for various complex membrane lipids. The protein's hydrophobic regions, evident in its amino acid sequence (particularly the stretches of hydrophobic residues like LLLSILIYLPAFVA), suggest membrane association, which would be consistent with its function in lipid biosynthesis .

Understanding this protein's function provides insights into how S. islandicus adapts its membrane composition to maintain functionality at extremely high temperatures and acidic conditions.

What are the implications of high-frequency recombination driven by conjugative plasmids in Sulfolobus islandicus?

The discovery of plasmid-mediated high-frequency recombination in S. islandicus has significant implications for understanding archaeal genome evolution and horizontal gene transfer. The integrated conjugative plasmid pM164 increases the frequency of marker exchange near its integration site in a manner dependent on the plasmid-encoded TraG protein . This mechanism creates localized "hotspots" of recombination, similar to the Hfr (high frequency recombination) mechanism in bacteria.

Key implications include:

• Genome architecture influence: The non-uniform recombination rates across the S. islandicus chromosome suggest that plasmid integration sites could influence genome architecture over evolutionary time .

• Species definition: Previous studies have shown that closely related groups of S. islandicus can maintain different levels of gene flow, fitting the biological species definition. Differences in recombination between "species" groups (such as the "Red" group) may be influenced by the presence and location of these conjugative elements .

• Horizontal gene transfer: The high efficiency of plasmid transfer (99% success rate observed in some experiments) provides a robust mechanism for horizontal gene transfer in archaea .

• Experimental applications: This mechanism can be harnessed for genetic engineering, allowing directed recombination at specific genomic loci by utilizing the appropriate conjugative elements.

These findings challenge the notion that recombination is uniform across archaeal genomes and suggest that mobile genetic elements play a crucial role in shaping genomic diversity and evolution in S. islandicus populations.

How can structural predictions inform research on the UPF0290 protein's function?

Although detailed structural information for the UPF0290 protein M1425_1364 is not explicitly provided in the available sources, researchers can leverage its amino acid sequence to generate structural predictions that inform functional hypotheses:

• Transmembrane domain analysis: The sequence MSIAYDLLLSILIYLPAFVANGSGPFIKRGTPIDFGKNFVDGRRLFGDGKTFEGLIVALTFGTTVGVIISKFFTAEWTLISFLESLFAMIGDMIGAFIKRRLGIPRGGRVLGLDQLDFVLGASLILVLMRVNITWYQFLFICGLAFFLHQGTNYVAYLLKIKNVPW contains several hydrophobic stretches that likely form transmembrane domains, consistent with a membrane-associated enzyme involved in lipid biosynthesis.

• Catalytic domain identification: Comparative analysis with other CDP-alcohol phosphatidyltransferase family members can identify conserved residues that may form the catalytic site for the CDP-archaeol synthase activity.

• Thermostability features: As a protein from a hyperthermophile, structural predictions should reveal features contributing to thermostability, such as:

  • Increased number of salt bridges

  • Higher proportion of charged amino acids on the surface

  • More compact hydrophobic core

  • Reduced loop regions

• Experimental validation approaches: Based on structural predictions, researchers can design:

  • Site-directed mutagenesis of predicted catalytic residues

  • Truncation studies to identify functional domains

  • Chimeric proteins to test domain functions

• Structural biology techniques: Given the protein's relatively small size (166 amino acids), it would be an excellent candidate for structural determination using X-ray crystallography or NMR, particularly if expressed with the His-tag for purification .

These structure-based approaches can guide hypothesis-driven research to elucidate the precise molecular function of this protein within the unique lipid biosynthesis pathways of S. islandicus.

What challenges might arise when expressing hyperthermophilic proteins in mesophilic hosts, and how can they be addressed?

Expressing hyperthermophilic proteins like the UPF0290 protein from S. islandicus in mesophilic hosts such as E. coli presents several challenges:

The standard approach used for the recombinant UPF0290 protein involves expression in E. coli with an N-terminal His-tag . The His-tag facilitates purification while minimally affecting protein structure. For functional studies, researchers should verify that the recombinant protein retains its thermostability and activity at high temperatures, despite being expressed in a mesophilic host.

If expression in E. coli fails to produce functional protein, alternative approaches include:

• Homologous expression in related Sulfolobus species using the genetic tools described previously

• Expression in other thermophilic hosts such as Thermus thermophilus

• Cell-free protein synthesis systems supplemented with archaeal chaperones

What are common pitfalls in genetic manipulation of Sulfolobus islandicus and how can they be overcome?

When working with genetic manipulation systems in S. islandicus, researchers commonly encounter several pitfalls:

• Low transformation efficiency:

  • Ensure cells are in mid-logarithmic growth phase

  • Optimize electroporation parameters (voltage, resistance)

  • Use freshly prepared competent cells

  • Pre-warm recovery media to 75°C before adding transformed cells

• Selection issues:

  • Verify the functionality of selection markers before use

  • Ensure proper concentration of selection agents (uracil, agmatine, 5-FOA)

  • Allow sufficient incubation time (7-14 days) for colony development

• Off-target CRISPR effects:

  • Carefully design protospacers to minimize off-target binding

  • Verify specificity using bioinformatic tools

  • Screen multiple transformants to identify those with intended edits only

• Plasmid instability:

  • Use plasmids with appropriate origins of replication for Sulfolobus

  • Maintain selection pressure throughout growth

  • Consider integration into the chromosome for stable maintenance

• Temperature sensitivity during manipulation:

  • Perform room-temperature steps quickly

  • Pre-warm all media and plates

  • Use water baths set to exact temperatures

  • Use Gelrite® instead of agar for plating at high temperatures

• Verification challenges:

  • Design primers carefully accounting for GC-rich regions

  • Use polymerases optimized for GC-rich templates

  • Sequence verify all constructs before and after transformation

By anticipating these challenges and implementing the suggested solutions, researchers can significantly improve the success rate of genetic manipulation experiments in S. islandicus.

How can researchers optimize culture conditions for consistent growth of Sulfolobus islandicus?

Optimizing culture conditions for S. islandicus is critical for reproducible research outcomes. These hyperthermophilic acidophiles require specific conditions:

For consistent growth:

• Standardize inoculum preparation:

  • Always use mid-logarithmic phase cultures (OD600 of 0.3-0.5)

  • Ensure uniform cell density for inoculation

  • Maintain glycerol stocks at -80°C for long-term preservation

• Optimize incubation conditions:

  • Use water baths rather than air incubators for more precise temperature control

  • Maintain humidity to prevent evaporation during long incubations

  • Place cultures in tightly closed plastic boxes during incubation

• Monitor growth parameters:

  • Track growth curves to establish consistent doubling times

  • Document pH changes during growth

  • Standardize harvesting points based on growth phase rather than absolute time

• Special considerations for genetic work:

  • When performing mating assays, equalize optical densities of partner strains before mixing

  • Allow 15-minute room temperature incubation before shifting to high temperature for conjugation

  • For plating transformants, use both selective and non-selective media to calculate transformation efficiency

Following these guidelines will help ensure reproducible growth and experimental outcomes when working with S. islandicus cultures.

What are emerging applications of the UPF0290 protein in biotechnology and fundamental research?

The UPF0290 protein from S. islandicus has several promising applications at the intersection of biotechnology and fundamental research:

• Thermostable enzyme applications:

  • As a potential CDP-archaeol synthase, this enzyme could be used to synthesize archaeal-like lipids for specialized liposome formulations with enhanced thermostability

  • Applications in drug delivery systems that require stability at elevated temperatures

  • Potential use in high-temperature industrial processes requiring lipid modification

• Membrane engineering:

  • Engineering bacterial or eukaryotic membranes with archaeal lipid components to increase thermostability

  • Creating hybrid membrane systems with novel properties for biotechnological applications

  • Developing temperature-resistant cell factories for industrial bioprocessing

• Evolutionary biology:

  • Investigating the evolution of lipid biosynthesis pathways across the three domains of life

  • Understanding adaptations that enable life in extreme environments

  • Exploring the lipid world hypothesis in the context of the origins of cellular life

• Structural biology:

  • The compact size (166 amino acids) makes this protein an excellent candidate for structural studies of thermostable membrane-associated enzymes

  • Insights into structure-function relationships in extremophilic proteins

  • Understanding the molecular basis of protein thermostability

• Synthetic biology:

  • Incorporation into minimal cell designs for high-temperature applications

  • Development of orthogonal membrane systems for synthetic cells

  • Creation of temperature-switchable biological circuits

As research on this protein advances, we can expect to see its application in developing novel biotechnologies that exploit its unique properties as a component from an extremophilic organism.

How might integrating genetic and biochemical approaches advance our understanding of Sulfolobus islandicus?

Integrating genetic and biochemical approaches presents a powerful strategy for advancing our understanding of S. islandicus biology:

• Functional genomics integration:

  • Use CRISPR-Cas genome editing to create targeted mutations in genes like M1425_1364

  • Combine with biochemical characterization of the resulting mutant phenotypes

  • Correlate genomic variations with biochemical differences between S. islandicus strains

  • Apply systems biology approaches to model metabolic networks

• Protein-protein interaction networks:

  • Identify interaction partners of UPF0290 protein using techniques adapted for thermophiles

  • Create tagged versions of the protein using the genetic tools described earlier

  • Map complete interaction networks for lipid biosynthesis pathways

  • Correlate with transcriptomic and proteomic data

• Evolution of extremophilic adaptations:

  • Compare recombination patterns near and distant from plasmid integration sites

  • Identify selection pressures on genes involved in thermoadaptation

  • Correlate genetic patterns with biochemical adaptations

  • Develop models for the evolution of thermostability in proteins and membranes

• Horizontal gene transfer dynamics:

  • Utilize the high-frequency recombination system to study gene transfer dynamics

  • Track the movement of mobile genetic elements within populations

  • Correlate genetic exchange with biochemical adaptations

  • Model the impact of recombination on genome evolution

• Synthetic biology applications:

  • Engineer S. islandicus strains with novel biochemical capabilities

  • Develop genetic circuits functional at high temperatures

  • Create reporter systems for studying gene expression in extreme conditions

  • Design minimal archaeal genomes based on essential biochemical pathways

By integrating these approaches, researchers can build a more comprehensive understanding of how genetic mechanisms and biochemical processes jointly enable S. islandicus to thrive in extreme environments, potentially revealing principles applicable to both fundamental biology and biotechnological applications.

What new genetic tools or methodologies would further advance research on hyperthermophilic archaea?

Several emerging genetic tools and methodologies could significantly advance research on hyperthermophilic archaea like S. islandicus:

• Expanded CRISPR toolbox:

  • Development of CRISPR interference (CRISPRi) systems optimized for archaea

  • CRISPR activation (CRISPRa) tools for upregulating gene expression

  • Base editing technologies adapted for high GC content genomes

  • Prime editing systems functional at high temperatures

  • Multiplexed CRISPR systems for simultaneous editing of multiple targets

• Advanced transformation methods:

  • Liposome-mediated transformation protocols optimized for hyperthermophiles

  • Development of natural competence induction in Sulfolobus species

  • Virus-like particle delivery systems for genetic material

  • Nanomaterial-based transformation methods stable at high temperatures

• Expanded marker systems:

  • Additional selectable markers beyond pyrEF and apt

  • Development of antibiotic resistance markers functional at high temperatures

  • Fluorescent and luminescent reporters optimized for archaeal expression

  • Split marker systems for improved selection stringency

• High-throughput approaches:

  • Random mutagenesis libraries for S. islandicus

  • Barcode-enabled genetic screens at high temperatures

  • Droplet microfluidics compatible with extreme pH and temperature

  • Deep mutational scanning of archaeal proteins

• Synthetic biology platforms:

  • Standardized genetic parts (promoters, terminators, RBSs) for archaeal systems

  • Cell-free expression systems derived from archaeal components

  • Genome transplantation methods for archaea

  • Minimal genome design and synthesis for hyperthermophiles

• In situ genetic methods:

  • Techniques for studying gene expression in natural hot spring environments

  • Environmental sampling and immediate genetic analysis

  • Methods to track horizontal gene transfer in natural archaeal communities

  • CRISPR-based lineage tracing in wild populations